Pregnant women who develop breast cancer also do not have worse rates of cancer recurrence than other young breast cancer patients, according to research in the journal Cancer.

ATLANTA — Pregnant women who develop breast cancer do not have worse odds of death or of cancer returning than other young breast cancer patients, a new study has found.

The study is one of the largest to look at whether breast cancer hits pregnant and recently pregnant women harder than other women. It contradicts some smaller, earlier studies that suggested maternity made things worse.

"If we can get them early, we can treat them aggressively and have good and promising outcomes for both woman and child," said the study's lead author, Dr. Beth Beadle of M.D. Anderson Cancer Center.

The Houston hospital has the world's largest registry of pregnant breast cancer patients and their children.

A breast cancer diagnosis is frightening for any woman, and particularly terrifying for a pregnant woman. It presents complicated decisions about how to treat the mother-to-be without causing harm to the fetus. Some doctors recommend abortion so they can focus on treating the woman.

In the new study published today in the journal Cancer, researchers analyzed data from 652 women ages 35 and younger who were treated for breast cancer at M.D. Anderson from 1973 to 2006.

The study group included 104 women with pregnancy-associated cancers -- 51 who had breast cancer during pregnancy, and 53 who developed the illness within a year after pregnancy.

The rates of cancer recurrence, cancer spread and survival were about the same for the women with pregnancy-associated breast cancers as they were for the other women, the researchers found. The researchers calculated the rates for 10 years after the cancer diagnosis.

The women who were pregnant had tumors at a more advanced stage, probably because women and their doctors may have discounted breast changes, attributing them to breast feeding or pregnancy, the researchers believe.

Generally, breast cancers are more aggressive in younger women, and survival rates are significantly lower. Although age may be a factor, it's not clear that pregnancy is: There was no evidence in the new study that tumors grew faster in the pregnant women, said Beadle, a radiation oncologist.

Radiation -- which is dangerous to a fetus -- is commonly used in mammography and breast cancer treatment. But ultrasound can be used to look for breast tumors instead. And surgery and certain kinds of chemotherapy can treat the cancer without causing harm to the fetus.

Still, breast cancer treatment remains a complicated medical situation that can depend on the severity of the cancer and how far into the pregnancy the woman is, said Dr. Ruth O'Regan, an associate professor at Emory University's Winship Cancer Institute in Atlanta.

"It's quite complicated, but all of us have been able to treat pregnant women successfully," O'Regan said.

The study did not present data on how well the children did. Other research at M.D. Anderson has not found developmental problems in those children, Beadle said.